The present invention relates to the utilization of a water cushion specifically adapted for utilization as a coupling device between the body of a human being on one hand and an apparatus for contactless lithotripsy on the other hand.
Contactless lithotripsy is a specific technology developed in recent years and concerns the destruction and comminution of concrements such as kidney stones in the body of the living being such as a human patient. In this technology shock waves are generated and focused onto and into the concrement in that body. The generation and focusing of such a shock wave is carried out within a device that is basically water filled and the problem exists to couple that device, e.g. to the body of the patient. If the device is a self contained unit which is physically separated and separable from the human being then some form of coupling is needed by means of which the shock waves generated in the equipment and device can be transmitted or coupled into the body of the human being. In earlier technologies the patient was placed in a water tub; hence the body of the patient was in immediate and direct contact with water which served as coupling fluid. The device by means of which the shock waves were generated included equipment with water filled cavities and the water of the cavities was in immediate and direct fluid conductive and exchanging contact with the water of the tub. This way a continuious uninterrupted transmission path was generated between the physical location of shock wave generation which shock waves were transmitted immediately and directed from the point of generation, into the coupling fluid namely water, and the transmission for the shock waves i.e. the water provided a continuous uninterrupted interface free transmission path to the skin of the patient. Even if for reasons of containment, some kind of membrane closed off the shock wave reflector cavity, the water in the tub provided a gapless transmission to the skin of the patient.
On the other hand it is apparent that this kind of arrangement is from an overall point of view voluminous and a more compact overall arrangement is desirable obviating the need for placing the patient into a water tub. There is still present the basic concept of generating a shock wave within a particular fluid and that shock wave has to be transmitted into the human body so that some form of coupling structure is needed. From an equipment point of view it is certainly advisable and advantageous to construct and design the equipment such that the shock wave generation is carried out in a self contained unit which is physically separable from the body of the human being without to put it in somewhat primitive terms, water pouring out all over the place. The liquid in the shock wave generation device should be kept separate and apart from the equipment that is self contained. On the other hand the shock waves as generated have to leave that equipment and be coupled into the body of the human being. For this some form of intermediate structure is needed and that is the purpose and function of the invention. The intermediate coupling device that couples the shock wave generator to the body of the human being will be a water cushion and details of such a water cushion constitute the object of the invention. Specifically the shock wave generator including focusing chamber, an immediate and direct shock wave source including a liquid medium for the shock waves is separated from the outside world by means of a membrane which has as its basic function the containment of the liquid i.e. water in which the shock wave is generated. That membrane is physically separated and separable from the body of the human being and some form of intermediary is needed to provide for shock wave transmission from the shock wave generating and focusing device into the body of the human being. To place that membrane right next to and into an immediate physical contact with the skin of the human being may seem to be the immediate solution to this problem. Such a "solution" is not satisfactory for the simple reason that an immediate contact between that membrane and the body of the human being cannot be assured and it is moreover uncertain as to how the propagation path from the shock wave generator into the human being will in fact continue from this complex interphase. A water cushion therefore has to be interposed which, in a multidimensional fashion, establishes an adaptable transmission path for the shock waves.
A specific problem was encountered that if one places some form of water cushion in between the patient and the shock wave generator-membrane a certain pressure is exerted by that water cushion upon the body of the human being. Whenever for some reason or another there is a change in position of the equipment vis-a-vis the patient by the water pressure that is exerted upon the patient, that pressure variation moves ever so slightly organs of the patient in the vicinity of the area of contact and that entails in cases movement of the concrement to be destroyed in the body, so that the position of that concrement vis-a-vis the shock wave and generating equipment becomes uncertain and dependent upon any possible variations in water pressure that is exerted on the body of the human being on account of the requisite coupling. It should be noted that this problem is not encountered (or to a much lesser degree) if the patient and the equipment are submerged in a water filled tub wherein, so to speak and from a hydrostatic point of view, an overall equilibrium can be established readily which in terms of transmission of shock waves establishes as homogenous a propagation medium as possible. But on the other hand it was outlined above that the cumbersomeness of the water filled tub is an aspect which for reasons of overall practicality one wants to get away from.